1. Field of the Invention
The present invention relates to a light-emitting diode light source apparatus configured as an assembly of a plurality of light-emitting diode elements and able to be used as a light source in various kinds of lighting.
2. Description of the Related Art
Conventionally, an LED (LIGHT-EMITTING DIODE) element, which is a compound semiconductor, has been widely used as a light source apparatus, taking advantage of its features of long operating life and potential for miniaturization. Moreover, the development of a blue color emitting LED element formed from a gallium nitride system compound semiconductor or the like has led to advances in commercialization of a white color emitting or pseudo-white color emitting light source apparatus. Furthermore, a high brightness high output light source apparatus designed with consideration for heat dissipation of the LED element is also commercially available. In addition, since there is a limit to the amount of light emitted by a single LED element, there is disclosed an LED or LED light source unit in which a plurality of LED elements are electrically connected to a single substrate to obtain a greater amount of light (refer, for example, to JP 2006-295085 A).
FIG. 11 shows a conventional LED light source unit 100. This LED light source unit 100 is provided with an elongated insulating substrate 101, a plurality of LED elements 110 arranged in a line at intervals in a long direction of the insulating substrate 101, a metal plate (not shown) fastened to a lower surface of the insulating substrate 101, and so on, the plurality of LED elements being mounted on the metal plate. Provided on an upper surface of the insulating substrate 101 are a pair of electrode patterns 104 formed by printing or the like. This pair of electrode patterns 104 includes two electrodes 102a and 102b for external connection provided at respective one ends of the pair of electrode patterns 104, the electrode patterns extending in a line along the long direction of the insulating substrate 101 on both sides of the plurality of LED elements 110 from the respective electrodes 102a and 102b, convex portions 103a and 103b for wire bonding to the LED elements 110 being formed on the electrode patterns on both sides of each of the LED elements 110.
The plurality of LED elements 110 are connected to the adjacent convex portions 103a and 103b by wires 111. As a result, each of the LED elements 110 is connected in parallel to the two electrodes 102a and 102b for external connection. When a drive voltage is supplied to the electrodes 102a and 102b, a drive current flows in each of the LED elements 110, whereby all of the LED elements 110 light up concurrently. Each of the LED elements 110 is sealed by a light-transmitting sealing resin 105, for example, and thereby mechanically and electrically protected.
The above-described conventional LED light source unit 100 has the plurality of LED elements 110 disposed in a line and can simultaneously light up the plurality of LED elements 110, and thus allows a relatively large amount of emitted light to be obtained. In addition, this conventional LED light source unit 100 allows a wide variety of forms of light sources to be easily formed by, for example, disposing a plurality of the LED light source units in a line, or two-dimensionally.
However, with the above-described conventional LED light source unit 100, the plurality of LED elements 110 are disposed in a line and the light emitting area thus becomes an elongated rectangular shape. Although optical design is made relatively easy by aligning a plurality of the above-described elongated rectangular LED light source units 100 to form a light emitting area of substantially square shape, gaps occur between the LED light source units 100 when aligned in plurality, the LED light source units 100 being separate bodies, which makes it difficult to increase the density of LED elements overall and is a barrier to obtaining a light source apparatus of higher lumen density.
Moreover, assuming the case where a lighting apparatus is installed with LED light source units 100 having a square shaped external shape as described above, since a lighting apparatus is generally bulb-shaped of substantially spherical shape, internal space efficiency of the lighting apparatus deteriorates leading to increased size of the lighting apparatus.
FIG. 12 shows in frame format one example of the case where a plurality of the conventional elongated rectangular LED light source units 100 are disposed two-dimensionally and installed on a base of a bulb-shaped lighting apparatus as a square shape compound light source unit. As shown in FIG. 12, five elongated rectangular LED light source units 100 are aligned to form the square shape compound light source unit, the compound light source unit being disposed inside a supporting frame 120 which is a portion of the base of the bulb-shaped lighting apparatus, the bulb-shaped lighting apparatus having a circular cross-sectional shape. Now, this leads to semicircular wasted spaces S1-S4 being formed in four places between the compound light source unit which is square and the supporting frame 120 which is circular as shown, and it can be understood that space efficiency with the square shape of LED light source units 100 is poor. Due to the above, and in consideration of the shape of the conventional lighting apparatus, there is need for a high brightness high output LED light source apparatus of easy optical design, high lumen density, and good space efficiency.